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The phone is a remarkably complex, simple device,
and very rarely ever needs repairs, once you fix them. Dan/Panther

Starting off in the hobby trying to understand the key system arena will be a bit difficult, because you do not yet have the more basic understanding of general telephony. But, your questions and understanding, so far, indicates that you are starting to get it quite nicely.

Rest of quote omitted, read up to see Victor's message.

I am fine with ringers of course, I never realized that there were different ring duration's and pauses between rings, that is very interesting, thanks for sharing this. I have been reading many places over the web and find that many people seem to want to configure using buzzers and so this makes me think that they were well used. I, once I gain a good understanding of how this operates, I can look at later possibly getting something like this configured.

- I have absolutely put together a 118a Ring Generator and the 551C It has the interrupter so I think I am good to go on "RING" output. I am planning to add one CO, this I would think would need to ring at least one phone.

Where I am now: - Western Electric 551C, 28D2 PS, KS-19175 L1 Interrupter - 118a Ring Generator on the way, its shipped. (Will use zip ties to strap down). I will actually have 2 more of these, didnt realize I picked up two, anyone need one of these NOS? - phones right now and will have two more in a couple of days. 3-2564's(waiting on 2), 1-564HD(565H* double marked) and 1-565HKM - I have 4 amphenol cables coming and some extra 25 pair cable also on the way. - Pre wired 66block with a single female amphenol, as understand I may not be able to use this. - 66 Block punch down tool, got this today!

Based on another post here: - I will be removing the 415's, I need a couple more SAN/BAR 4000F KTU's, know anyone? - Is it possible to have you analyze the wire connections in the back of this if I were to take some close up pictures? These extra wires do not appear to be factory but could be. They are also soldered and not wire wrapped the way so many of the other connections are, they are different types of wire. Tracing them, they run from each of the KTU's-interrupter-PS-block. On the block, I see where many things have been jumped also. Hey, this could all be standard stuff, however, its better to have an expert look it over.

Over all, I do want to understand fully what I am doing and how this awesome 1a2 technology is supposed to work. It would be great to put this together with era wire based on WE Standards, or even Bell. The correct color codes I plan as much as possible to follow so if for example one of you guru's see it, you would know exactly what your looking at. With that, I would be learning the same as many of the techs worked on these in the field. I would get a lot of satisfaction in putting it together the way it is supposed to be put together.

I completely appreciate that, I am somewhat verbose as well and some of these messages are gaining some ground quick. I think for now, the easiest way to get these working with the equipment I have is in my opinion the best solution for now. Once I get my head around what I have, I can then start looking into "upgrading". I do like the enhanced DICM though, this sounds involved. For nostalgic purposes though putting this together in the same method as many offices ran them is what I would like to tackle first.

Thank you for putting this together, very informative, as is most all of your posts. Learning a lot fast.

Hi digoxy118I 100% agree with Victor, 1A2 is a simple concept but you do need to have some basic understanding. I got my 1st 1A2 at 14 1/2, at that time there was no public info, late 1970's. I had to figure it out on may own, today the internet has a lot of great info and also some bad info. I recommend first to connecting 1 line and one phone to get a understanding, if you try to wire up the entire system at the 1st time you may frustrate yourself. Locate the 25 Pair color code (Google) and print it out, the 1st line only needs 6 (1st 3 pairs) wires connected between the phone and the 551 (KSU) the telephone line is only 2 wires, The rotary and ITT 2564 will not be concerned about the polarity of the phone line going to the line card (400)type KTU. The Western Electric phones will not dial out if the line polarity is reversed. I would hold off on the intercom until you have a better understanding of the system, The ITT 1a2 key manuals are simpler than the BSP's for basic understanding. The BSP was trained tech's, the beginners had simple layout and learned from lab instructors and senior installers, As Victor said there was a reason for everything. No one will be critical of you learning. Enjoy you self. P.S. I may have the 118 mounting bracket. Phil

Hello Phil, (et/all)

Thanks for your feedback, greatly appreciated and you have some excellent points here. I think I am going to agree with you on starting with one line, this would be something that I can focus on. First, let me ask, the "BSP" is this the reference to the "Practice" I have been tying to decode? If so, where might I find anything at that is ITT 1a2 Manuals, are these online also? I will google for this in a moment but if you have a website with a downloadable links would be great.

There should be a few 25 pair amphenol 1a2 cables coming. - Should I connect this directly to the block in the KTU or connect it to an external block? - How would this be done in the field? - Is there any documents you can recommend that will show me the connections for line1 to the KSU block? - I will look for and obtain the 25 pair color code, I would want this to be true to WE! I may have to clarify what I find. - If I am going to work with line1, does it require a 400KTU in J1 (first KTU slot)?

If you have one of these brackets, that would be absolutely amazing. I have looked everywhere for one of these, as so many have said they are made from Unobtainium. I am also looking for a deep sea 551C Cover, I think these may all be submerged in the North Atlantic. Rumor has it, one of these was crushed between the Titanic and and a chunk of ice.

I have printed out and have been reading through "Bell System Practice (BSP!) AT&TCo Standard Section 518-215-407, Issue 2, June 1981". This is the most recent one I could find, I found one also from the 70's that is nice to compare and understand the differences between the 551A/B and C. All good Stuff.

If there is yet another "bible" I should have at my fingertips, please let me know what they are and I will certainly find them and print them, really enjoy delving into this stuff, way to much fun.

I did study your ad on eBay, I look at it often, every time I search for 1a2, Western Electric 551C. You dont know how close I came to smashing that buy it now button, I wanted to build one though, as fun as it would have been to drop a working system on the table, I wouldn't understand what I was looking at. That system I think is good for a business slap it in and go. With all that said though, you might have good insight on what I may need to buy, and, may have something stocked. Let me know.

If you don't know about Telephone collectors international, they have a library with lots of Phone information. If you think that your interest will grow, then join and you will have many others that share you phone interest.

Look for ITT 601a Ksu. Also Itt 512a will work as well, Itt had a clear and easy to read layout of how to wire the phones and KSU, Please note they did things much different than bell. But its great info, after you study it then the BSP may be easier to understand.

Here is a link to a large system, Please be sitting down, This is what a nice size system looked look. Yes this is a present installation as of 8-2017 working 1A2 system, I have about 300 lines of 1A2, But I also have my own Central office to supply dial tone, when finished ill have more that 300 key phones wired to it,This was built to show off large key systems, and also I like phones.

Phil, this is your 1a2 hobby system? I remember seeing this page a few weeks ago, started with the picture of I guess you standing in a isle. This system is huge! way more than I would ever put together. How do you find the time to work with that? Watched a couple of video's, commented on one as well, subscribed of course.

here are the pics you requested... I hope they help..... the first 3 are of my San-Bar 6610 and the rest are the 551-C

Hey John,

It doesn't appear you are using much on the 551C? I see you have a small RJ11 Jack installed onto the Ring Generator Bracket (The bracket I dont have). Is that for the CO or for a set? Good quality pictures to, looks like that KSU is great shape. Do you have much terminating on the KSU Block? If so, you have any close up shots of your connections? Sorry so many questions. Do you have a thread on here somewhere you display and discuss your 551C?

The SAN/BAR unit looks really good to.

Thank you for taking the time to post these pictures. I kept looking for a "LIKE" Button on the 551 pics, there isnt one! :)

Wanted - Picture sharing of your Western Electric 551. Wanted - Recommended acquisitions of equipment to play with that utilizes the 551.

Set (phone) connection to KSU.

The reason I am working so close in detail here is that I would like this set up as it would be in the field. If one of you guys who worked on this equipment were to see my set up, I would want to know that it is done correctly and know that it what would be expected in the field, please let me know if this sounds right, and, if you have any suggestions, comments, recommendations or anything at all, feel free to chime in, i really want to do this right in the spirit of respect of these older 1a2 systems.

The common method from what I understand in connecting a 25 pair amphenol connector from a set (a phone) to a KSU is through a 66 Block.

Here is what I would like to do:Step 1 - A. Connect a female 25 pair amphenol connector to an external 66 block (I will call this a station block). - B. Plug a set (a phone) into the female amphenol connector for testing.

Step 2 - A. Run connect wires from the KSU 551C Block to the newly wired station 66 block.

Questions: (1) 1-A, What type of 66 Block should I use? I have asked for a few different blocks from a user here on the forum and may be able to acquire 4 row 50, 6 row 50 I think is what they are. Which type would be used in the field connecting this equipment? If phone set amphenol 25 par connectors are connected to these, would it make sense to use the 6 row 66 blocks?

(2) 1-A, I have dug deep to try and answer this question through practices, images posted on the web, asking in forums and have yet to connect the dots on this question. When connecting the 25 pair to the station block, do I follow the standard color set wht/blu, blu/wht, wht/org, org/wht, wht/grn, grn/wht etc? If I am right, these would connect from pin 1 of the block all the way to pin 50 following the standard code (posted the 50 pair below), this should be the same up to 25 pair right?

(3) 1-A, Once the station block is installed I should then be able to add 2-3 25 pair amphenol female set connection points using the color code?

(4) 1-A, I should then be able to daisy chain these station connection blocks by punching down a 25 pair from Block Station block A to Block Station block B, then systematically add more 25 pair amphenol connectors to block B?

(5) 2-A, This has been on my head for the last 24 hours, its like a nail driven into the frontal lobe. In the BSP ISS 2 Section 518-215-407 Fig3 draws out the pin connection of the line connections pretty clearly "TO KEY TELEPHONE SETS". This shows Lines 1-4 connections on rows 1 through 24. Is this all that needs to be connected to a 25 pair cable that is run externally connected to a station block? How about Audible Signal Connections? Is there anything else I need to pick up and carry out?

(6) 2-A, When connecting the 25 pair that is to lead out to the station block, is it traditionally done in the 551C block to connect this 25 pair on the left side or the right side of the block?

(7) 2-A, Is there on this forum somewhere someone has simplified the standard connections to 1a2 KSU connections? I would think it would be something like this? (see added image, color code stamped on this would be very helpful).

(8) 2-A, Would it be feasible, practical or/and any type of standard to wire a single amphenol connector to the 551 block to carry out to a station block that is equipped with a female pre wired?---------

I am without a doubt over the top appreciative of any knowledge shared with my project. I understand this is a lot to be asking from a forum group. My willingness to learn this 1a2 system can only be carried out by the few individuals who would like to teach a young pad-wan like myself. Thank you for any assistance what so ever, even the smallest bits can cast light on so much.

I have no knowledge of the 1A2 system to share but I wanted to comment. I think it is great to see a new person with such an intense interest. This is what our forum is all about, we have gotten a little bit away from it recently so I, for one, am glad to see it again! I know there are plenty of experienced people here who will be happy to help and I look forward to maybe learning something along with you. I have always believed the only stupid question is the one you don't ask!

I have no knowledge of the 1A2 system to share but I wanted to comment. I think it is great to see a new person with such an intense interest. This is what our forum is all about, we have gotten a little bit away from it recently so I, for one, am glad to see it again! I know there are plenty of experienced people here who will be happy to help and I look forward to maybe learning something along with you. I have always believed the only stupid question is the one you don't ask!

Hey Harry, thanks for the feedback. I do delve into some of this stuff pretty heavily. There are so many people here that like to converse on these subjects, it really makes it fun. I do indeed have a lot of questions, I get by with a little help from my friends, albeit, new friends.